An MQD, also known as Medallion Qualification Dollars, is a way to calculate the dollar amount spent by a member on the flight. They are earned from ticket purchases, seat upgrades, and eligible Delta Vacations packages. Moreover, if you are wondering, "How are Delta MQDS Calculated", it depends on the base fare and carrier-imposed surcharges, excluding taxes and fees. For further insights on this, contact the customer service of Delta Airlines or check out the blog linked above.